Wearable articles such as diapers having wetness sensing are useful to provide wetness information for use or for reference by service or medical personnel. For example, diapers having electronic wetness sensing are useful to health care professionals because the wetness state of a diaper can be determined without actual diaper inspection. The availability of diapers having electronic wetness sensing arrangements has drastically improved the quality of life of bed-confined patients or the elderly having mobility problems.
Wetness detection in wearable article is typically facilitated by way of resistance or capacitance measurements. To facilitate wetness detection, wetness sensing electrodes are usually formed on the wearable article and the instantaneous capacitance or resistance values across the electrodes are then measured to determine the wetness of such a wearable article. However, conventional wetness detection systems only provide very raw information on whether a wearable article has been wetted, but are unable to provide more precise or detailed wetness information such as the level, degree or specific location of wetness.
Conventional wetness detection in wearable articles using the resistance detection approach has known shortcomings, such as, for example, unable to provide information on the extent of wetness. On the other hand, conventional wetness detection using capacitance detection is prone to external interference due to the small capacitance across the electrodes, because the capacitance across the electrodes is typically in the region of several picofarads. Furthermore, measurement of such a small capacitance means the need of a high frequency oscillation circuitry which adds to detection circuit complexity and is vulnerability to interference. Similar shortcomings are also present in conventional electrolyte level detection systems using resistance or capacitance measurements, and anode oxidation is a known problem.